JP2002232385A - Ofdm receiver using diversity adaptive array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the deterioration due to a multipath, using a diversity adaptive array. SOLUTION: Propagation parameters such as arrival wave number, arrival wave power and time change of the power variation are obtained every OFDM symbol from correlation detection information, power measurement information and norm integrated values every received symbol, the propagation path condition is estimated, based on these parameters, to determine which operation mode is suited to the propagation environment between the adaptive array signal processing and the diversity signal processing, and the operation mode is changed for the diversity or adaptive array signal processing according to the propagation path condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to OFDM (Orthogonal Frequency Divisio) in which the frequency of each carrier is set so that each carrier is orthogonal to each other within a symbol section.
The present invention relates to a receiver of the n multiplexing (orthogonal frequency division multiplexing) type, and more particularly to an OFDM receiver that performs diversity reception using signals received by a plurality of antennas arranged so that correlation between signals is reduced.

More specifically, the present invention relates to an OFDM receiver configured to be small in size by performing selective diversity reception by selectively using a received signal having the highest signal power among a plurality of received signals, and in particular, to an OFDM receiver having a small size. When the propagation path environment is multipath, adaptive array signal processing for removing interference waves is performed, and in other propagation environments, selection diversity can be switched.
The present invention relates to an OFDM receiver using an adaptive array.

[0003]

2. Description of the Related Art In recent years, the spread and demand of mobile communications such as mobile phones and vehicle-mounted phones have been remarkably developing. Now everyone is using mobile communication devices and is being recognized as a necessity in social life.

[0004] When wireless transmission is performed in a mobile propagation environment, deterioration of transmission quality due to fading or multipath is a particular problem.

As a technique for realizing high-speed and high-quality wireless transmission, "OFDM (Orthogonal Frequency Division)
Multiplexing: orthogonal frequency division multiplexing) is expected. The OFDM system is a type of multi-carrier (multi-carrier) transmission system, and the frequency of each carrier is set such that the carriers are orthogonal to each other within a symbol section. An example of information transmission is that information transmitted in serial is transmitted serially at every symbol period lower than the information transmission rate.
A plurality of data output by parallel conversion are assigned to each carrier and modulated for each carrier, and the inverse FFT is performed on the plurality of carriers, thereby maintaining the orthogonality of each carrier on the frequency axis and the signal on the time axis. Convert to and send. For example, each carrier is BPSK (Binary Phase S)
hift Keying) It is assumed that the information transmission rate is 256
When serial / parallel conversion is performed at a 1 / symbol period, the total number of carriers becomes 256, and inverse FFT is performed on 256 carriers. Demodulation is performed in the reverse operation, that is, FFT is performed to convert a signal on the time axis into a signal on the frequency axis, perform demodulation corresponding to each modulation method for each carrier, and perform parallel / serial conversion to obtain an original serial signal. This is performed by reproducing the transmitted information. It has been experimentally confirmed that the OFDM transmission system has good transmission characteristics even with a delayed wave.

In the OFDM transmission, one symbol period is longer than that of a single carrier transmission system having the same transmission capacity. Therefore, the fading resistance against multipath fading or selective fading with a large delay time difference between incoming waves is strong. There are features. However, in a multipath composed of a plurality of arriving waves, when the delay time of the interfering wave with respect to the main wave exceeds the guard interval or when the power ratio (D / U) of the main wave and the interfering wave is large, the demodulated signal is output. However, there is a problem that the error rate of the demodulated signal deteriorates even in flat fading in which the delay time difference between the arriving waves is small.

[0007] To solve the deterioration due to multipath, adaptive array signal processing for removing interference waves is effective. On the other hand, in order to solve the deterioration due to flat fading, diversity reception using signals received by a plurality of antennas arranged so as to reduce the correlation between signals is effective. The main methods include selection diversity for selecting a received signal having the highest signal power among a plurality of received signals, maximum ratio combining diversity for demodulating the plurality of received signals and performing maximum ratio combining, and the like.

[0008] Comparing with the apparatus scale, the former selection diversity requires only one receiving system after selecting a received signal, but the latter has a maximum ratio combining diversity because a plurality of receiving systems up to demodulation are required. . In comparison with the diversity gain, the former selection diversity is about 2 dB worse than the latter maximum ratio combining diversity. For this reason, when performing diversity reception, it is necessary to determine which of the former and the latter is better in terms of the desired device scale and diversity gain.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a small-sized, excellently-structured selective diversity receiver that selectively uses a received signal having the highest signal power among a plurality of received signals. An object of the present invention is to provide an OFDM receiver.

A further object of the present invention is to make it possible to efficiently estimate the propagation path from the distribution of arriving waves without changing the device block configuration, perform adaptive signal processing when the propagation path environment is multipath, and perform other signal processing. An object of the present invention is to provide an excellent OFDM receiving apparatus using a diversity adaptive array that can be switched by selecting a diversity in a propagation environment.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and a first aspect of the present invention is directed to an OFDM (Orthogonal Frequency Division Multiplexing) including pilot symbols received by a plurality of antennas. A channel estimating means for estimating a channel on the basis of an arriving wave distribution for a signal, and determining a channel environment based on the result of the channel estimation, and performing adaptive signal processing when the channel environment is multipath. Signal processing means for performing signal processing by switching a receiving device provided with a common block for selection diversity in the case of another propagation path environment, and an OFDM receiving device using a diversity adaptive array. It is.

[0012] According to the OFDM receiver using the diversity adaptive array according to the first aspect of the present invention, the operation mode is dynamically switched based on the propagation path environment, and when the propagation path environment is multipath. Performs adaptive signal processing, and in the case of another propagation path environment, can perform signal processing by switching a receiving device provided with a block having a common selection diversity.

Further, a second aspect of the present invention relates to a plurality of OFs.
An OFDM receiving apparatus using selective diversity for selectively using a DM (Orthogonal Frequency Division Multiplexing) received signal, wherein a receiving antenna and a signal received via the receiving antenna are down-converted from an RF frequency band to a baseband signal. And a plurality of reception systems each including a digital conversion unit for A / D converting the down-converted baseband signal into a complex digital signal, and weighting the complex digital signal when performing adaptive signal processing. And, when diversity is performed, one of the complex digital signals from each reception system is selected. When adaptive signal processing is performed, the complex digital signals weighted by the weight calculator are added. A selection synthesis unit, and a complex digital signal output from the selection synthesis unit An FFT unit that performs Fourier transform for one period of the OFDM symbol in accordance with the FFT window timing to generate received symbols of parallel carriers, and a correlation calculation for a complex digital signal output by the selective combining unit using a guard interval signal And a correlation detection unit that outputs correlation detection information including FFT window timing information, the peak number of correlation signals, peak power, and the like, and a demodulation unit that demodulates received symbols of parallel carriers corresponding to each reception system, A pilot symbol is extracted from received symbols for each OFDM subcarrier for several parallel carriers output by the FFT unit, a propagation path is estimated, and an arrival angle of an incoming wave based on the pilot symbol is estimated. A reference signal corresponding to the arriving wave with strong signal power A reference signal generation unit for generating a complex digital signal from each receiving system, power measurement is performed for each of the complex digital signals, and a magnitude comparison is performed to extract a complex digital signal having the highest power, and the reference signal and the extracted complex digital signal are extracted. And a diversity adaptive array signal processing unit for calculating an optimum weighting factor for a received signal in each receiving system by using the OFD using the diversity adaptive array.
M receiving device.

Here, when performing the adaptive signal processing, the weight calculating section weights the complex digital signal from each receiving system by the optimal weight coefficient calculated by the diversity adaptive array signal processing section. And outputs the result of the addition as a composite complex digital signal to the correlation detection unit and the FFT unit. The correlation detection unit performs correlation detection using a repetition pattern of a guard interval section, and generates correlation detection information including FFT window timing information, the number of peaks of a correlation signal, peak power, and the like. Window timing information is stored in the FF
The correlation detection information is output to the T section and the correlation detection information is output to the reference signal generation section. Further, the FFT unit includes:
OFDM according to the FFT window timing information
Fourier transform is performed for each symbol to generate parallel carrier reception symbols, which are output to the demodulation unit and the reference signal generation unit. The demodulation unit performs demodulation for each received symbol of the parallel carrier. Further, the reference signal generation unit extracts a pilot symbol from a plurality of received symbols of the parallel carrier, generates the same sequence as a pilot symbol sequence at the time of transmission, and calculates a norm for each received symbol based on a difference between the two. Calculate, estimate the arrival angle of the arriving wave based on the norm integral values that have been respectively integrated, generate a reference signal based on the estimated value and the complex digital signal, and send the reference signal to the diversity adaptive array signal processing unit. Output. Further, the diversity adaptive array signal processing unit calculates a weight coefficient based on the complex digital signal and the reference signal for each guard interval section and outputs the weight coefficient to the weight calculation unit.

On the other hand, when performing diversity, the diversity adaptive array signal processing section
The power is measured for the complex digital signals from the respective receiving systems, and the powers are compared with each other to determine the complex digital signal having the highest power, and output to the selection / synthesis unit as path selection information. In addition, the selection / synthesis unit selects only one complex digital signal according to path selection information for a complex digital signal not weighted by the weight calculation unit. Then, FFT, demodulation, and correlation detection are performed on the complex digital signal.

Therefore, according to the OFDM receiving apparatus using the diversity adaptive array according to the second aspect of the present invention, both the diversity and the adaptive array signal processing can be realized by a common block configuration. The scale can be saved.

Further, the reference signal generating section is configured to calculate correlation information based on correlation detection information input from the correlation detection section, power measurement information input from the diversity adaptive array signal processing section, and a norm integral value for each of the received symbols. Propagation path parameters including the number of arriving waves, the arriving wave power, the time transition of power fluctuation, etc. are obtained for each OFDM symbol,
Estimating the channel conditions based on the channel parameters,
Since the operation mode of the adaptive array signal processing or the diversity is determined according to the estimation result, it is possible to switch between the diversity and the adaptive array signal processing according to the propagation path condition.

When the reference signal generation unit switches the operation mode to diversity and determines that synchronization is not obtained from the correlation detection information input from the correlation detection unit, the reference signal generation unit sets a preset integration period or timing. While measuring the power of the complex digital signal from each receiving system and comparing the magnitudes of the respective power measurement results, selecting the one with the larger value and outputting it to the correlation detector to perform the correlation detection, Since the estimation of the propagation path condition is started after the acquisition, and the operation mode is switched to the adaptive array signal processing or the diversity, the efficiency of the signal processing up to the acquisition of the synchronization can be improved.

In the case where the operation mode is diversity, the reference signal generation unit includes: correlation detection information input from the correlation detection unit; power measurement information input from the diversity adaptive array signal processing unit; Based on the norm integral value, the power measurement cycle and the measurement timing are determined, and each time they are changed, the power is switched and the power measurement of the complex digital signal is performed. This can be done according to the situation.

Further, when the operation mode is changed, the reference signal generation section continues to perform signal processing in the operation mode before the change until the boundary of the OFDM symbol immediately thereafter, and outputs a demodulated symbol of a parallel carrier. OFD
Since the operation after the boundary of the M symbol is operated in the changed operation mode, even when the operation mode is switched,
An OFDM symbol can be demodulated without interruption of a data sequence.

Still other objects, features and advantages of the present invention are:
It will become apparent from the following more detailed description based on the embodiments of the present invention and the accompanying drawings.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Before describing an OFDM receiving apparatus using a diversity adaptive array according to the present invention, a schematic configuration of an example of an OFDM transmitting apparatus for transmitting an OFDM signal will be described with reference to FIG.

As shown in FIG. 1, OFDM signal transmitting apparatus 100 includes a modulating section 101, a pilot symbol inserting section 102, a serial / parallel converting section 103, an IF
FT section 104, guard section insertion section 105, analog conversion section 106, RF section 107, transmission antenna 108
And a transmission control unit 109.

Upon receiving the transmission data, modulation section 101 performs modulation in accordance with the modulation information and timing supplied from transmission control section 109, and serially outputs modulation symbols.

[0026] Pilot symbol insertion section 102 inserts a known data sequence into a modulation symbol sequence as a pilot symbol in accordance with the pilot symbol insertion pattern and timing input from transmission control section 109.

The serial / parallel converter 103 converts serial data into parallel data corresponding to the number of parallel carriers according to the number of parallel carriers and the timing input from the transmission controller 109.

IFFT section 104 performs FFT according to the FFT size and timing input from transmission control section 109.
Inverse Fourier transform for FT size is performed.

[0029] The guard section insertion unit 105 includes the transmission control unit 1.
A guard signal such as a guard interval and a guard band is inserted in accordance with the guard interval size, guard band size, and timing input from step 09.

The digital transmission signal into which the guard signal has been inserted is subjected to quadrature modulation and A / D
The signal is converted, up-converted by transmission RF section 107, and transmitted from transmission antenna.

An OFDM receiving apparatus using the diversity adaptive array according to the present invention can receive, for example, an OFDM signal transmitted from the above-described OFDM transmitting apparatus 100. Hereinafter, an OFDM receiving apparatus to which the diversity adaptive array according to the present invention is applied, and a description will be given of an apparatus configuration and operation characteristics of the OFDM receiving apparatus using two receiving antennas with reference to the drawings. .

FIG. 2 shows an OFDM using a diversity adaptive array according to one embodiment of the present invention.
2 schematically shows the configuration of the receiving apparatus 200.

The OFDM receiver 200 using the present diversity adaptive array shown in FIG. 1 has two receiving antennas, each having a carrier frequency of one.
A ULA configuration installed at a distance of 1/2 wavelength is adopted. Therefore, when the incoming wave is a plane wave, it is possible to separate two incoming waves having the angles of arrival θ ₁ and θ ₂ from the vertical direction of the antenna. In addition, selection diversity using two antennas can be performed.

In FIG. 2, reference numerals 201 and 20
2 is a receiving antenna. The signals received by the respective receiving antennas are down-converted from RF frequency bands to baseband signals by RF units 203 and 204, respectively.

The digital converters 205 and 206 convert the analog baseband signal down-converted by the respective RF units 203 and 204 into a complex digital signal using an A / D converter and a quadrature detector, and output the complex digital signal.

The buffers 207 and 208 temporarily store the complex digital signals output from the digital converters 205 and 206, respectively, and output them at appropriate timing.

When performing the diversity, the weight calculators 209 and 210 do not process the complex digital signals input from the buffers 207 and 208. On the other hand, when performing adaptive array signal processing, complex multiplication of weighting coefficients W ₁ and W ₂ set by the diversity adaptive array signal processing unit 216 (described later) and each complex digital signal is performed, and the result is output. I do.

The selection / synthesizing section 211 has a diversity adaptive array signal processing section 216 at the time of diversity.
When a complex digital signal determined to be optimum is selected from the two reception systems according to the diversity adaptive array information sent from the receiver (described later) and adaptive array signal processing is performed, the weight calculator 209 is used.
The weighted complex digital signal input from 210 is added.

FFT section 212 performs Fourier transform on the complex digital signal that has been selectively combined and input from selection and combining section 211, and outputs received symbols for the number of parallel carriers.

The correlation detection section 213 performs correlation detection on the complex digital signal that has been selectively synthesized from the selection synthesis section 211, and outputs FFT window timing information and a correlation detection result.

[0041] Demodulation section 214 demodulates the received symbols for the number of parallel carriers input from FFT section 212 and outputs demodulated data.

The reference signal generation unit 215 is an FFT
Pilot symbols are extracted from received symbols for the number of parallel carriers input from section 212 and
DOA (Direction of Arrival) based on the symbol
Of Array) to generate a reference signal that is a reference for adaptive array signal processing.

The diversity adaptive array signal processing section 216 operates based on the correlation detection information sent from the correlation detection section 213 and the arriving wave detection information input from the reference signal generation section 215. More specifically, when diversity is performed, each buffer 207, 208
The power of each of the complex digital signals input from is measured for a preset period and compared, and the one with the larger power is selected as path selection information. When performing adaptive array signal processing, each of the antennas 201 and 20 is used by the reference signal and the complex digital signal.
2 is calculated for each of the received signals from the receiver ₂ and output as the optimum weighting coefficients W ₁ and W ₂ , and the above-mentioned path selection information and the control information such as the diversity or adaptive array signal information are subjected to adaptive array control. Output as information.

The operation characteristics of the OFDM receiver using the diversity adaptive array configured as described above will be described below.

The signals received by the receiving antennas 201 and 202 are converted into baseband signals by the RF units 203 and 204, respectively,
Output to 206.

The digital converters 205 and 206 output A /
Each receiving antenna 201 by the D converter and the quadrature detector,
A baseband complex digital signal corresponding to 202 is generated and output to respective buffers 207 and 208.

The baseband complex digital signals stored in the buffers 207 and 208 are input to the weight calculators 209 and 210, the reference signal generator 215, and the diversity adaptive array signal processor 216 in accordance with the respective output timings. Is done.

When performing the diversity, the weight calculators 209 and 210 respectively use the buffers 207 and 20 respectively.
No processing is performed on each of the complex digital signals input from 8. When performing adaptive array signal processing, the respective weighting factors W ₁ and W calculated by the diversity adaptive array signal processing unit 216 for the complex digital signals 1 and 2 input from the buffers 207 and 208, respectively. _{The result} is multiplied by 2 and output as complex digital signals 1 'and 2'.

The selection / synthesizing unit 211 uses the diversity / adaptive-array signal processing unit 216 to control the power of the complex digital signals 1-2 when performing diversity according to the diversity / adaptive-array information sent from the diversity / adaptive-array selecting unit 216. One of the complex digital signals 1 'or 2' determined to have a high received power from the measurement result is selected. When performing adaptive array signal processing, the baseband complex digital signals 1 'and 2' input from each of the weight calculators 209 and 210 are added and output as a complex digital signal selectively synthesized.

The complex digital signal thus selectively combined is subjected to Fourier transform by the FFT section 212 every time one cycle of the OFDM symbol is input to generate received symbols for the number of parallel carriers. Output to the generation unit 215. The demodulation section 214 performs demodulation for each carrier and outputs demodulated data.

The complex digital signal selectively synthesized is subjected to correlation detection by the correlation detection section 213 using the repetition pattern of the guard interval section.
Correlation detection information such as FT window timing information, the number of peaks of the correlation signal, and the peak power is generated. The former FFT window timing information is FFT
The correlation detection information is input to the reference signal generation unit 215.

After the synchronization is established and the FFT starts operating normally, reference signal generating section 215 extracts pilot symbols from the received symbols for the number of parallel carriers, and outputs pilot symbols inserted by the transmitting apparatus. The same sequence as the symbol sequence is generated, a norm is calculated based on the difference between the two, and integration is performed on the norm for one OFDM symbol. Based on the norm calculation result and the correlation detection information sent from the correlation detection unit 213, a channel estimation such as whether or not the channel is in a multipath environment is performed. If it is determined that the environment is a multipath environment as a result of the propagation path estimation, the arrival angle (DO) of the arriving wave is determined based on the integral value for each OFDM symbol.
A: Direction Of Array) is estimated, and based on the estimated value and the signal obtained by delaying the complex digital signal input from each of the buffers 207 and 208 by one period of the OFDM symbol, it corresponds to the arriving wave having the strongest power. A reference signal to be generated is generated. On the other hand, if it is determined that the environment is not a multipath environment, the above-described DOA estimation and reference signal generation are not performed.

The reference signal and the arriving wave information such as the above-described propagation path estimation result and reference signal generation state are output to the diversity adaptive array signal processing section 216.

The diversity adaptive array signal processing section 216 performs an integral dump of power for each complex digital signal input from each of the buffers 207 and 208 for a predetermined cycle. If it is determined that the environment is flat fading based on the arriving wave information input from the reference signal generator 215 and the power measurement result, the power measurement result is compared,
The comparison information is determined such that the one with the higher received power is selected from the two reception systems described above. If it is determined that the environment is a multipath environment, a reference matrix input from the reference signal generation unit 215 receives a correlation matrix R _xx and its inverse matrix R _xx ^-1 for a part corresponding to a guard interval section of the complex digital signal. The optimum weight W _opt is calculated by calculating the correlation vector r _co based on the signal and the complex digital signal and taking the product of the inverse matrix R _xx ^-1 and the correlation matrix R _xx.
Is calculated. The optimum weight is output to each of the weight calculators 209 and 210 as weight coefficients W ₁ and W ₂ , and is updated for each guard interval.

The signal processing by the diversity adaptive array according to the present embodiment is performed by the diversity adaptive array signal processing section 216 and the integration dump section which are schematically shown in FIGS. 3, 4, 5 and 6. This is realized by the cooperative operation of the functional modules 303, the reference signal generator 215, and the selector / synthesizer 211. Hereinafter, a schematic configuration and operation characteristics of each functional module will be described with reference to the drawings.

FIG. 3 is a block diagram showing a schematic configuration of the diversity adaptive array signal processing section 216.

In the figure, reference numeral 301 denotes a complex digital signal 1 input from each of the buffers 207 and 208.
2 is a vector generation unit that converts each of them into a vector type.

Reference numeral 302 denotes a correlation matrix calculator for calculating a correlation matrix R _xx from a vector-type complex digital signal input from the vector generator 301.

Reference numeral 303 denotes a gain, the number of integrations, and the number of integrations sent from the diversity adaptive array signal control unit 310 for each element of the correlation matrix R _xx .
An integration dump unit that performs integration dump according to integration and dump timing.

Reference numeral 304 denotes the integral dump unit 3
03 to the inverse matrix R _xx from the correlation matrix R _xx sent from
^This is an inverse matrix calculator that calculates ^-1 .

Reference numeral 305 denotes a correlation vector calculation unit that calculates a correlation vector r _co based on the vector type complex digital signal and a reference signal input from the diversity adaptive array signal processing unit 216.

Reference numeral 306 denotes an integral dump unit for performing an integral dump of each element of the correlation vector r _co in accordance with the gain, the number of integrations, the integration, and the dump timing sent from the adaptive array signal control unit 310. .

Reference numeral 307 denotes a weight determining unit for calculating an optimum weight W _opt corresponding to a received signal received by each of the receiving antennas 201 and 202.

Reference numeral 308 denotes a power measuring section for measuring the power of the vector type complex digital signal input from the vector generating section 301 for each power measuring cycle transmitted from the diversity adaptive array signal processing section 310. is there.

Reference numeral 309 indicates that when diversity is performed, a comparison is made between the power measurement results of the vector-type complex digital signal and the reception antenna 201 or 2
02 is a comparing unit that selects the one with the larger power out of 02 and outputs the result to the diversity adaptive array signal processing control unit 310 as the path selection information.

The diversity adaptive array signal processing control section 310 controls the coefficients and operation timing of each block based on the arriving wave detection information input from the reference signal generation section 215, and performs the above-described path selection information and power measurement. The control information such as the result is output to the other function modules as the diversity / adaptive array control information.

FIG. 4 shows an integral dump unit 303 in FIG.
306 shows a schematic configuration. Reference numeral 401 in the figure is a selector that selects 0 in the case of reset or dump timing transmitted as a control signal, and otherwise selects data input from the gain unit 402.

The gain section 402 amplifies the data input from the delay section 403 with the gain setting value sent by the control signal. The delay unit 403 stores data input from the adding unit 404.

The adder 404 adds data sent from the selector 401 and input data sent from the outside.

The storage unit 405 latches the data sent from the adding unit 404 and outputs a dump value according to the dump timing sent as a control signal.

FIG. 5 shows a schematic configuration of the reference signal generator 215 shown in FIG. Reference numeral 501 in the figure is a pilot signal generation unit that generates the same sequence _ptx as the pilot symbol sequence generated by the pilot symbol insertion unit 102 of the OFDM transmission device (see FIG. 1).

Reference numeral 502 calculates the norm of the transmission pilot symbol sequence _ptx generated by pilot signal generation section 501 and the reception pilot symbol sequence _prx extracted from the reception symbols input from FFT section 212. It is a norm calculation unit.

Reference numeral 503 denotes a gain transmitted from a reference signal generation control unit 509 (described later),
An integration dump unit that performs integration dump according to the number of integrations, integration, and dump timing.

Reference numeral 504 denotes the integral dump unit 5
A comparison unit that compares the integration result of the norm input from the control unit 03 with the arrival wave direction determination threshold value transmitted from the reference signal generation control unit 509.

Reference numeral 505 denotes an arrival wave direction DOA [θ ₁ , θ ₂ ] based on the comparison result in the comparison unit 504.
Is a direction-of-arrival setting unit that sets the value of.

Reference numeral 506 indicates that each buffer 20
A delay unit that stores the complex digital signals 1 and 2 input from the reference signal generation units 7 and 208 and outputs the stored complex digital signals according to the timing sent from the reference signal generation control unit 509.

The reference numeral 507 is the direction of arrival DOA [θ ₁ , input from the direction-of-arrival setting unit 505 described above.
θ ₂ ] and each of the complex digital signals 1 and 2 sent from the delay unit 506 to generate a reference signal.

Reference numeral 508 denotes a reference signal generation control unit, which is a diversity adaptive information such as correlation detection information input from the correlation detection unit 213 and a power measurement result of a complex digital signal input from the diversity adaptive array signal processing unit 216. Based on propagation path information such as whether or not a multipath environment is obtained from the array information and the norm calculation value input from the norm calculation unit 502, the coefficients and operation timing of each block are controlled, or the presence / absence and estimation of the arrival direction estimation are performed. It outputs information such as incoming wave detection information such as accuracy.

FIG. 6 shows a schematic configuration of the selection / synthesis unit 211. In the figure, reference numeral 601 denotes an adder that adds the complex digital signals 1 ′ and 2 ′ input from the weight calculators 209 and 210 when the adaptive array signal processing is performed.

Reference numeral 602 indicates that when diversity is performed, one of the above complex digital signals 1 ′ and 2 ′ is converted based on the selection signal sent from the selection and synthesis control unit 604. It is a selection section to be selected.

Reference numeral 603 indicates that the signal added by the adder 601 is output when the adaptive array signal processing is performed, while the selector 602 is selected when the diversity is performed. It is a selector that outputs a signal.

Next, the operation characteristics of the diversity adaptive array signal processing section 216 and the reference signal generation section 215 configured as described above will be described.

FIG. 7 shows an example of the diversity signal processing timing when diversity is performed. FIG. 8 shows an example of signal processing timing by the adaptive array when performing the adaptive array signal processing.

In the following description, the OF in this embodiment is described.
As shown by the complex digital signals in FIGS. 7 and 8, the DM signal is composed of an OFDM symbol D _n and a guard interval G _{n obtained} by copying the second half of the OFDM symbol by the guard interval. _n ,
D _n in this order (where n = 1, 2, 2
..., N). Here, T _g is the guard interval length [se
c], and T _s is one period of the OFDM symbol [sec]
It is. In these timing examples, it is assumed that there is no clock error or frequency offset between transmission and reception.

The diversity signal processing is executed when the operation mode is diversity. FIG.
The example of the power measurement timing shown in (d) corresponds to the diversity adaptive array signal processing unit 2 shown in FIG.
16 shows a process of obtaining path selection information in selection diversity performed using the power measurement unit 308 and the comparison unit 309 in FIG.

FIG. 7A shows the power measurement timing at the time of initial synchronization. Since the correct FFT window has not been detected at the time of the initial synchronization, the integration cycle and integration timing are as shown in T _d (1) to T _d (2) in FIG.
Power measurement and comparison are performed using a predetermined initial value, and path selection information in selection diversity performed using power measurement section 308 and comparison section 309 is obtained. Then, based on this path selection information, the selector 602 selects the received signal having the larger power measurement result among the complex digital signals 1 ′ or 2 ′, Outputs digital signal.

If the synchronization is successfully acquired, the correlation detecting section 21
3 outputs synchronization acquisition information to the reference signal generation unit 215. As a result, the power measurement timing is set to T in FIG.
_{As shown in d} (3) to _Td (5), it is changed to coincide with the boundary of the FFT window. After that, the power measurement is FF
It is performed from the top of the T window. The power measurement timing of the power measurement unit 308 in this process is shown in FIG.
As shown in c1 to c5 in (a).

FIG. 7B shows the power measurement timing when the FFT size is changed. Here the power measurement is O
It is performed for the period of the FDM signal.
It is assumed that the size switching timing is known.

In the example shown in FIG. 7B, T _d (n) to T _d
The signal transmitted at the OFDM signal period 1 corresponding to the section (n + 1) has a double FFT size T _d (n + 2) to T _d
This shows that the OFDM signal period 2 having (n + 4) has been switched. More specifically, T _d (0) -T
_d (1) and T _d (1) to T _d (2) correspond to OFDM symbols before FFT size switching, and T _d (2) to T _d
(4) and T _d (4) to T _d (6) are OFs after switching
It corresponds to a DM symbol.

The power measurement timing starts from the beginning of the next OFDM signal cycle from which the FFT size switching information is obtained, that is, from T _d (2) in FIG.
The power measurement performed in the M signal cycle 1 is now performed in the section of the OFDM signal cycle 2. The power measurement timing in this process is as shown by c1 to c4 in FIG.

FIG. 7C shows the power measurement timing for guard interval elimination. If a long guard interval such as 1/4 of the OFDM signal period is set, or if the transmission quality fluctuates greatly, FFT
Eliminating the power in the guard interval section outside the window from the integration range allows higher accuracy power measurement. The example illustrated in FIG. 7C illustrates a case where the power measurement is switched from a cycle including the guard interval to a cycle in which the guard interval portion is removed.

In the complex digital signal shown in FIG. 7 (c), power measurement including a guard interval is performed in the section shown by T _d (0) to T _d (2), and then T _d (2)
Power measurement except for the guard interval is performed in the section indicated by _Td (5). In the example shown in the figure, a reset signal is set in a portion corresponding to a guard interval. The power measurement timing in this process is as shown by c1 to c4 in FIG.

FIG. 7D shows an example of power measurement timing using transmission quality information in a flat fading environment. The power measurement in this case is shown in FIG.
(C) shows a process of switching the power measurement cycle at an arbitrary timing, and is effective in a flat fading environment without frequency distortion. In the complex digital signal shown in FIG.
_{In the} section shown from _d (0) to _Td (2), the OFDM signal cycle
Power measurement is performed in one cycle, and the following _Td (2) to _Td (5)
In the section shown in (1), power measurement is performed in a half cycle of the OFDM signal cycle. This corresponds to a case where the Doppler frequency changes from low to high in flat fading. The integration cycle timing of the integration dump unit in this process is as shown by c1 to c9 in FIG.

On the other hand, the adaptive array signal processing is executed when the operation mode is the adaptive array.

When the complex digital signal [a-1] is received, a 1 OFDM symbol delay signal such as [a-2] is generated by the delay unit. And [a-1] and [a-2]
When the correlation is taken, since the two patterns have the same pattern in the section from T _c (n) to T _d (n), the correlation can be detected. In the correlation detection unit 213, this section T
Correlation detection is performed using _c (n) to T _d (n) as the correlation detection execution section, and correlation detection information such as FFT window timing information, the number of peaks of the correlation signal, and the peak power is obtained.

The norm integral [a-3] is calculated in the interval T _d (n−
1) to T _d (n), and the integrated value is dumped at time T _d (n). In the example shown in FIG. 8, the norm is calculated every time. However, the norm is calculated after the initial synchronization is obtained according to the information from the correlation detection unit 213, or when the multipath detection is performed.
Since it is performed when a situation such as a change in the angle of arrival of an incoming wave is observed, it is not necessary to constantly calculate the norm.

Assuming a multipath of two waves and arriving angles θ ₁ and θ ₂ respectively, the integrated value n_su
m [θ ₁ , θ ₂ ] is given by the following equation.

[0098]

(Equation 1)

Here, i _max is the total number of pilot symbols in one OFDM symbol, p _tx (i) is a transmission pilot symbol sequence, and p _rx (i) is a reception pilot symbol sequence. Further, the norm corresponds to the distance between the transmission pilot symbol and the reception pilot symbol as shown in FIG.

When the norm integration result n_sum [θ ₁ , θ ₂ ] is dumped, the arrival angle of the arriving wave is estimated by comparing it with a preset threshold value or by using a convergence algorithm such as the steepest descent method. As a result, when the determination condition for the arrival angle estimation is satisfied, the corresponding arrival angles θ1 and θ2 are updated as the estimation result.

In the update of the reference signal [a-4] in FIG. 8, the arrival angles are estimated for the norms 1 to 4 which are n_sum [θ ₁ , θ ₂ ] dumped at each time.
Among them, the norm 1 and the norm 3 show that the determination conditions for the arrival angle estimation are satisfied. In this case, the corresponding angles of arrival have been updated to DOA1 and DOA3. on the other hand,
The norm 2 indicates that the previously set arrival angle DOA1 is used because the determination condition for the arrival angle estimation is not satisfied.

When the angle of arrival is updated, the value is used from the updated correlation detection execution section at the next timing. In [a-4] of FIG. 8, the updated DOA1 and DOA3 are used from time _Tc (2) and _Tc (4), respectively.

The reference signal is the set arrival angle D
It is generated for the guard interval section of the OA and one OFDM symbol delay signal shown in [a-2] of FIG.
That is, in FIG. 7, G _n ′ in the section from T _c (n) to T _d (n)
It is done about.

The reference signal is obtained as follows.
Can be That is, the arriving wave vector is s =
[S₁, S_Two] And a complex delay delayed by one OFDM symbol.
X (t−T)_s) =
[X₁, X_Two], The angle of arrival θ of the incoming wave ₁, θ_TwoThe step represented by
Suppose that there is no influence of noise with the arranging matrix as A
And the following equation holds.

[0105]

(Equation 2)

Assuming that the reference signal is r _ref = s ₁ , s ₁ is given by the following equation.

[0107]

(Equation 3)

When the angles of arrival θ ₁ and θ ₂ are determined as described above, the reference signal r _ref can be calculated using the 1 OFDM symbol delay signal.

The adaptive array signal processing is performed using a reference signal input every correlation detection execution section. Here, the optimum weight W _opt for the received signal is calculated, and the weight coefficients W ₁ and W ₂ are updated. For example, FIG.
In the adaptive array signal processing using the reference signal r _ref corresponding to the angle of arrival DOA1 determined at T _d (2), the adaptive array signal processing is performed in the section C2 of [a-5]. The optimum weight W _opt is a correlation matrix R _xx = E [x (t) x obtained from a signal vector x composed of complex digital signals.
^H (t)] of the inverse matrix R _xx ^-1 and the correlation vector r _co = E [x
(T) r _ref ^* (t)] is calculated over the correlation detection execution section, and after integration for one section, that is, at the timing of T _d (n), is calculated according to the following equation.

[0110]

(Equation 4)

The optimum weight W _opt is a correlation detection execution interval T during the execution of the adaptive array signal processing.
_{c (n) ~ T d (} n) calculated weighting factor for each can be updated with the performed time T _d (n), weight calculation is performed on the complex digital signal is used as a weighting factor later.
The optimal weight once updated in this way is held until the next time the value is updated.

The optimal weight W _opt is a correlation detection execution section T _c during the execution of the adaptive array signal processing.
A weight coefficient is calculated for each of (n) to T _d (n), updated at time T _d (n), and used as a subsequent weight coefficient to calculate a weight for the complex digital signal.
The optimal weight once updated in this way is held until the next time the value is updated.

Next, a processing procedure for setting the operation mode of the diversity adaptive array signal processing will be described with reference to the flowchart shown in FIG. Here, the setting of the operation mode such as the diversity or adaptive array signal processing and the switching procedure are shown with the reception start when the power is turned on, immediately after the sleep mode, or when the signal is resynchronized after the synchronization is lost.

First, in step S1, the correlation detection section 213 performs correlation detection and outputs correlation detection information as undetected. Also, the reference signal generator 215
Does not perform the operation and outputs the arriving wave information as undetected. Further, the diversity adaptive array signal processing section 216 measures the power of each of the complex digital signals 1 and 2 of each receiving system, compares the two with each other, and determines the larger one as the path selection signal. In addition, the operation mode is set to diversity, and it is output as diversity adaptive array control information together with path selection information.

Next, in step S2, it is determined whether or not synchronization has been obtained. If you didn't get sync,
The process returns to step S1 described above. If synchronization can be obtained, the process proceeds to the subsequent step S3.

In step S3, the correlation detecting unit 213 determines
The FFT window timing information and the number of peaks and the peak power of the correlation signal are output as correlation detection information based on the detected initial synchronization timing. In addition, the reference signal generation control unit 508, based on the correlation detection information,
Estimate the propagation path environment.

Next, in step S4, it is determined whether or not the estimated propagation path is in a multipath environment.

If it is determined that the propagation path is not in a multipath environment, the process proceeds to step S5. In this case, the reference signal generation unit 215 generates a reference signal, and outputs that the propagation path is not a multipath environment as arriving wave information. Further, the diversity adaptive array signal processing section 216 measures the power of each of the complex digital signals 1 and 2 from each of the receiving systems, compares the powers of the two, and uses the larger one as the path selection information. In addition, the operation mode is set to diversity, and it is output as diversity adaptive array control information together with path selection information.

On the other hand, if it is determined that the propagation path is in a multipath environment, the process proceeds to step S6. In this case, the reference signal generation unit 215 generates a reference signal, and outputs that the propagation path is a multipath environment as arriving wave information. Further, the diversity adaptive array signal processing section 216 performs signal processing with the operation mode being an adaptive array, and outputs this operation mode as diversity adaptive array information.

Next, in step S7, the correlation detection unit 2
Reference numeral 13 outputs the number of peaks and peak power of the detected correlation signal as correlation detection information. Further, the reference signal generation unit 215 performs a norm calculation in the norm calculation unit 502 regardless of the operation mode. Also, the reference signal generation control unit 5008 estimates the propagation path environment based on the calculation result of the norm and the correlation detection information.

In this specification, the case where two reception antennas are used has been described as an example. However, even when three or more reception antennas are used, the reception system using the two reception antennas as described above is used. This can be realized by extending to antennas. That is, the receiving antenna, the RF unit, the digital conversion unit, the buffer, and the weight calculating unit shown in FIG. 2 are provided by the number corresponding to the receiving antenna, and the reference signal generating unit and the adaptive array processing unit set the optimum weight for the number of the receiving antennas. If the necessary calculations can be performed, the functions and effects of the present invention can be similarly achieved. By increasing the number of antennas, diversity reception can reduce the probability of receiving a drop section due to fading. Further, in the adaptive array signal processing, although the processing amount of the optimal weight calculation increases, the resolution can be improved because the number of arriving waves for which the arriving wave direction can be estimated increases.

[Supplement] The present invention has been described in detail with reference to the specific embodiments. However, it is obvious that those skilled in the art can modify or substitute the embodiment without departing from the spirit of the present invention. That is, the present invention has been disclosed by way of example, and should not be construed as limiting. In order to determine the gist of the present invention, the claims described at the beginning should be considered.

[0123]

As described above in detail, according to the present invention,
Without changing the device block configuration, it is possible to efficiently estimate the propagation path from the arriving wave distribution, perform adaptive signal processing when the propagation path environment is multipath, and switch the selection diversity in other propagation environments. An excellent OFDM receiving apparatus using the diversity adaptive array configured as described above can be provided.

According to the OFDM receiver using the diversity adaptive array according to the present invention, diversity and adaptive array signal processing can be realized by a common block configuration, and the configuration of the device can be simplified.

Further, according to the OFDM receiver using the diversity adaptive array according to the present invention, it is possible to switch between diversity and adaptive array signal processing according to the propagation path conditions, and to solve the problem of deterioration due to multipath. Can be eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an example of an OFDM transmitting apparatus that transmits an OFDM signal.

FIG. 2 shows an OFDM receiving apparatus 200 using a diversity adaptive array according to one embodiment of the present invention.
FIG. 2 is a diagram schematically showing the configuration of FIG.

FIG. 3 shows an OFDM receiving apparatus 200 using a diversity adaptive array according to one embodiment of the present invention.
FIG. 4 is a diagram showing a schematic configuration of a diversity adaptive array signal processing unit 216 which is a component of FIG.

FIG. 4 is an OFDM receiver 200 using a diversity adaptive array according to one embodiment of the present invention.
FIG. 4 is a diagram showing a schematic configuration of an integral dump unit which is a component of the embodiment.

FIG. 5 shows an OFDM receiving apparatus 200 using a diversity adaptive array according to one embodiment of the present invention.
FIG. 3 is a diagram showing a schematic configuration of a reference signal generation unit 215 as a component of FIG.

FIG. 6 shows an OFDM receiving apparatus 200 using a diversity adaptive array according to one embodiment of the present invention.
FIG. 3 is a diagram showing a schematic configuration of a selection / synthesis unit 211 which is a component of FIG.

FIG. 7 is a diagram showing an example of power measurement timing in an OFDM receiving apparatus 200 using an adaptive array according to one embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of adaptive array signal processing timing in an OFDM receiving apparatus 200 using an adaptive array according to one embodiment of the present invention.

FIG. 9 is a diagram showing an image of a norm in an OFDM receiving apparatus 200 using an adaptive array according to one embodiment of the present invention.

FIG. 10 is a flowchart showing a procedure for setting an operation mode of diversity adaptive array signal processing in an OFDM receiving apparatus using an adaptive array according to one embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 OFDM signal transmission apparatus 101 modulation section 102 pilot symbol insertion section 103 serial / parallel conversion section 104 IFFT
Unit 105 guard interval insertion unit 106 analog conversion unit 107 RF unit 108 transmission antenna 109 transmission control unit 201, 202 reception antenna 203, 204 RF unit 205, 206 digital conversion unit 207, 208 Buffers 209, 210: Weight calculation unit 211: Selection / combination unit, 212: FFT unit 213: Correlation detection unit, 214: Demodulation unit 215: Reference signal generation unit 216: Diversity / adaptive array signal processing unit 301: Vector generation unit, 302 ... Correlation matrix calculator 303 integration dumper 304 inverse matrix calculator 305 correlation vector calculator 306 integration dumper 307 weight determining unit 308 power measuring unit 309 comparison unit 310 diversity adaptive array Signal processing control unit 401 ... selector, 40 2 Gain section 403 Delay section, 404 Addition section, 405 Storage section 501 Pilot signal generation section, 502 Norm calculation section 503 Integration dump section, 504 Comparison section 505 DOA setting section, 506 Delay section 507: Reference signal calculation unit 508: Reference signal generation unit 601: Addition unit, 602: Selection unit 603: Selector, 604: Selection synthesis unit

Claims (8)

[Claims] 1. A propagation path estimating means for estimating a propagation path for an OFDM (orthogonal frequency division multiplexing) signal including pilot symbols received by a plurality of antennas based on an arrival wave distribution, and based on the propagation path estimation result. Signal processing means for determining a propagation path environment, performing adaptive signal processing when the propagation path environment is multipath, switching to diversity when the propagation path environment is another path environment, and performing signal processing. OFDM receiver using a diversity adaptive array. 2. An OFDM receiving apparatus using selective diversity for selectively using a plurality of OFDM (Orthogonal Frequency Division Multiplexing) received signals, comprising: a receiving antenna and a signal received via the receiving antenna in an RF frequency band. Performing adaptive signal processing, including a plurality of receiving systems each including an RF unit for down-converting a baseband signal from a digital signal to a baseband signal and a digital conversion unit for A / D converting the down-converted baseband signal into a complex digital signal Is a weight calculator for weighting the complex digital signal, and one is selected from the complex digital signals from the respective reception systems when diversity is performed, and each weighted by the weight calculator when adaptive signal processing is performed. A selection / synthesis unit for adding a complex digital signal, and an output from the selection / synthesis unit An FFT unit for performing a Fourier transform of one period of the OFDM symbol on the complex digital signal in accordance with a predetermined FFT window timing to generate a received symbol of a parallel carrier; and a guard interval part for the complex digital signal output by the selective combining unit. A correlation detection unit that performs correlation calculation using signals and outputs correlation detection information including FFT window / timing information, peak number of correlation signals, peak power, and the like, and demodulation of received symbols of parallel carriers corresponding to each reception system. Demodulation section, and OFDM for several parallel carriers output by the FFT section
A pilot symbol is extracted from a received symbol for each subcarrier, a propagation path is estimated, and the pilot symbol is extracted.
A reference signal generator for estimating an arrival angle of an incoming wave based on a symbol to generate a reference signal corresponding to an incoming wave having the strongest signal power, and performing power measurement on a complex digital signal from each receiving system. A diversity adaptive array signal processing unit that extracts the complex power digital signal having the largest power, calculates the optimum weighting factor for the received signal in each receiving system by the reference signal and the extracted complex digital signal, and An OFDM receiver using a diversity adaptive array, comprising: 3. When adaptive signal processing is performed, the weight calculation unit weights and adds the complex digital signal from each reception system using the optimum weight coefficient calculated by the diversity adaptive array signal processing unit. And outputting the addition result as a composite complex digital signal to the correlation detection unit and the FFT unit. The correlation detection unit performs correlation detection using a repetition pattern of a guard interval section, and outputs FFT window timing information and Generating correlation detection information including a peak number of correlation signals, peak power, and the like, outputting the FFT window timing information to the FFT unit, and outputting the correlation detection information to the reference signal generation unit; The O / O unit according to the FFT window timing information Performs a Fourier transform for each DM symbol to generate parallel carrier reception symbols and outputs them to the demodulation unit and the reference signal generation unit.The demodulation unit performs demodulation for each parallel carrier reception symbol. The reference signal generation unit extracts a pilot symbol from the plurality of received symbols of the parallel carrier, generates the same sequence as the pilot symbol sequence at the time of transmission, calculates a norm for each received symbol based on the difference between the two, Estimate the angle of arrival of the arriving wave based on the integrated norm integral value, generate a reference signal based on the estimated value and the complex digital signal, and output the reference signal to the diversity adaptive array signal processing unit, The diversity adaptive array signal processing unit performs the duplication for each guard interval. Based on the digital signal and the reference signal to calculate a weighting factor to output to the weight calculation section, using the diversity adaptive array according to claim 1, wherein the OF
DM receiver. 4. When diversity is performed, the diversity adaptive array signal processing section measures power of complex digital signals from each receiving system and compares the magnitudes of the complex digital signals to obtain a complex digital signal having the largest power. And outputs the same as path selection information to the selection / synthesis unit.The selection / synthesis unit selects only one complex digital signal according to the path selection information for the complex digital signal not weighted by the weight calculation unit, 2. The OFD using the diversity adaptive array according to claim 1, wherein FFT, demodulation, and correlation detection are performed on the selected complex digital signal.
M receiving device. 5. The reference signal generation section, based on correlation detection information input from the correlation detection section, power measurement information input from the diversity adaptive array signal processing section, and a norm integral value for each of the received symbols. OFD
The number of arriving waves, the arriving wave power, the propagation path parameters including the time transition of the power fluctuation, etc. are determined in units of M symbols, the propagation path conditions are estimated based on the propagation path parameters, and the adaptive array signal processing or The OFDM receiving apparatus using the diversity adaptive array according to claim 1, wherein one of the operation modes of the diversity is determined. 6. When the reference signal generation unit switches the operation mode to diversity and determines that synchronization is not obtained from the correlation detection information input from the correlation detection unit, the reference signal generation unit sets a preset integration period or timing. The power of the complex digital signal from each receiving system is measured at
Select the larger value and output it to the correlation detection unit to perform correlation detection, start the estimation of the propagation path condition after synchronization is obtained, and switch the operation mode to adaptive array signal processing or diversity. An OFDM using the diversity adaptive array according to claim 1,
Receiver. 7. When the operation mode is diversity, the reference signal generation unit includes: correlation detection information input from the correlation detection unit; power measurement information input from the diversity adaptive array signal processing unit; 2. The diversity according to claim 1, wherein the power measurement cycle and the measurement timing are determined based on the norm integral value, and the power measurement of the complex digital signal is performed by switching whenever necessary. -An OFDM receiver using an adaptive array. 8. When the operation mode is changed, the reference signal generation unit continues to perform signal processing in the operation mode before the change until the boundary of the OFDM symbol immediately thereafter, and outputs demodulated symbols of the parallel carrier. 2. The OFDM receiving apparatus using a diversity adaptive array according to claim 1, wherein the apparatus operates in the changed operation mode after the boundary of the OFDM symbol.